The goal of this proposal is to develop a fundamental understanding of structure and function of the art gene of HTLV-III/LAV. This study is relevant to elucidation of fundamental genetic regulatory mechanisms that govern viral gene expression and which may also govern the expression of cellular genes in normal and in cancer cells. The study is also relevant to the design of novel classes of anti-AIDS drugs. The art gene is a recently discovered gene of HTLV-III that is thought to encode a protein needed for a late stage of viral production, specifically the synthesis of the viral capsid and envelope proteins. Virus genetically defective for the art gene are incapable of replication, an observation that implies that anti-art drugs should prevent viral growth and therefore be useful for anti-AIDS therapy. Specific aims include: 1. Physical characterization of the art gene product. 2. Investigation of the mechanism of action of the art gene. 3. Investigation of the active sites of the art gene product. 4. Developmetn of a rapid biochemical screen for anti-art drugs.